Official definition

This U.S. industry comprises establishments primarily engaged in manufacturing power, distribution, and specialty transformers (except electronic components). Industrial-type and consumer-type transformers in this industry vary (e.g., step up or step down) voltage but do not convert alternating to direct or direct to alternating current. Illustrative Examples: Fluorescent ballasts (i.e., transformers) manufacturing Substation transformers, electric power distribution, manufacturing Distribution transformers, electric, manufacturing Transmission and distribution voltage regulators manufacturing Cross-References.